ELFH Flashcards
Which Mapleson system is most efficient for spontaneously ventilating patients
Mapleson A
What is the name of the co-axial version of Mapleson A circuit
Lack system
What is the volume of an adult reservoir bag in a breathing circuit
2L
What is a Jackson-Rees system
Mapleson F
Has an open ended reservoir bag which allows PEEP and controlled leak
Give 4 roles/benefits of a reservoir bag on breathing system
1- Allow higher peak inspiratory flow to be delivered as ventilator alone is not enough for normal respiration
2- Rough visual assessment of ventilating volume
3- provide PEEP
4- Prevent wastage of FGF during expiratory pause
How many multiples of minute ventilation does a Bain system require to prevent rebreathing during spontaneous ventilation
2-3X
(Mapleson D)
Why is Magill system inefficient during controlled ventilation
APL valve at patient side of circuit so most of expired gases are vented off.
What size are soda lime granules
4-8 mesh
What are the constituents of baralyme
80% Calcium hydroxide
20% Barium Hydroxide
Does soda lime produce more or less compound A during low FGF
More
What are the constituents of Sodalime
75% Calcium Oxide (CaO)
20% Water
3% Sodium hydroxide (NaOH)
1% Potassium hydroxide (KOH)
Why can FIO2 slowly decrease over time during low flow anaesthesia
If metabolic requirements exceed O2 supply in FGF the oxygen conc. in the system will start to decrease
What is the MAC of Nitrous Oxide
105%
How does water affect sodalite efficiency
Water is generated by the overall reaction of CO2 with soda lime but it’s presence or absence does not influence performance of sodalite
Can Nitrous Oxide be safely delivered using a quantiflex mixer? How does this work?
Yes.
Quantiflex mixer allows a full range oxygen/nitrous oxide mixtures to be administered from 21-100% oxygen so avoiding accidental hypoxic mixtures.
Why can nitrous oxide not be used as an anaesthetic agent by itself?
MAC is 105% so can’t deliver enough whilst also giving oxygen
What is the pin index of nitrous oxide
3, 5
What colour is the collar of a nitrous oxide cyllinder
French Blue
What is the difference between a Magill and Lack system
APL valve is at machine end in Lack system
In Lack system there is an inner co-axial tube for expired gas and FGF is on external limb.
What proportion of MV is required for spontaneous ventilation using Magill circuit
70% of MV
Summarise Cardiff Aldasorber
Canister containing charcoal that acts as passive scavenger. Absorbs anaesthetic gasses including isoflurane but not Nitrous oxide. Low resistance. Can be reactivated by heating to remove absorbed gasses. No indicator die so hard to tell when saturated.
When filled what percentage of the volume of a canister is taken up by sodalime granules
50%
Which anaesthetic gas causes production of Compound A in soda lime
Sevoflurane
Which 3 anaesthetic gases cause production of CO in soda lime
DIE
Desflurane
Isoflurane
Enflurane
What is the purpose of the gold lining of the rotameter
Anti-static
Define critical gas velocity
The velocity of a gas at which it changes from laminar flow to turbulent flow
How does helium reduce turbulent flow in respiratory system
Helium has lower density than air/O2. Reduces Reynolds number.
What effect can water vapour have on a Fleisch pneumotachograph
Water vapour can block pressure transducers or smaller tubes in the pneumotachograph
How does the length of a tube affect resistance to flow
Resistance is directly proportional to length of tube in laminar flow.
Flow = Pressure difference/ resistance
Flow = pressure difference X π R 4 / 8 X Viscosity x Length
How does temperature affect Reynold’s number
Increasing temperature decreases density of a gas which decreases Reynolds number
Can flow through an orifice be laminar
Flow through an orifice is always turbulent and affected by density
How does haematocrit affect flow in blood vessels
Reduced haematocrit = reduced viscosity of blood.
This increases flow (Hagen Poiseuille)
Increases likely hood of turbulent flow ( reducing viscosity increases Reynolds number)
How does flow affect resistance in laminar flow
Resistance is independent of flow when flow is laminar
How does flow affect resistance in Turbulent flow
Increase in flow causes an exponential increase in resistance
What is 1 torr equivalent to in mmHg
1 mmHg
What is 1 ATM equivalent to in cmH2O
1035 cmH2O
What is the mechanism of action of Clozapine
Partial agonist at D2 receptors
What is the difference between EC50 and ED50 of a drug
EC50: The dose of the drug required to cause 50% of maximal effect
ED50: The dose required to cause cause the therapeutic effect in 50% of the population
Is cAMP hydrophilic or Hydrophobic
Hydrophilic
List 4 mixed agonist - antagonist drugs
Pentazocine
Buprenorphine
Mirtazepine
Xameterol
How to you get the time constant from the rate constant
Time constant = 1 / rate constant
To what percentage of its initial activity does a negative exponential process fall after 1 time constant
37%
(1/e)
Which subunits make up an ACh receptor
2 alpha sub units
1 Beta sub unit
1 Delta sub unit
1 epsilon sub unit
How does the ACh receptor differ in the foetus compared to adult
The foetal receptor has a gamma sub unit instead of the adult epsilon sub unit
Which receptors does Midazolam act on
GABAa receptors
